KR102084612B1 - Improved biological waste water purification reactor and method - Google Patents

Abstract

The water to be treated and the oxygenous gases are subjected to ascending co-currents in the same reactor containing a volume of mobile, hollow carrier with a packed bed as the biological filtration material and a protective surface for the growth of the microbial membrane. A biological purification reactor and method sent are provided. The purge reactor 1 is lowered in the reactor by a space for expansion and removal of the sludge 2, a gas injection system 4, a fluid injection system 3, a porous holding sail 6 with respect to upward movement. A packed bed of particles retained in the part and a volume of mobile particles 10 located in the space for the expansion and removal of the sludge 2.

Description

IMPROVED BIOLOGICAL WASTE WATER PURIFICATION REACTOR AND METHOD

FIELD OF THE INVENTION The present invention relates to the field of biological wastewater purification, and more particularly to the field of biological wastewater purification of municipal wastewater, industrial wastewater and distribution water to be made of drinking water. The present invention specifically relates to an upflow (in the same reactor or biological filter in which the water and oxygen gas to be treated comprise a packed bed and a volume of movable carriers as the biological filtration material. ascending co-currents).

For example, it is known that the biological treatment of water consists in decomposing organic impurities by the action of purified or fixed, and purified biomass containing various microorganisms, such as bacteria, yeast, protozoa, welfare, and the like. In a method using free biomass such as activated sludge, considering that the concentration of the biomass is obtained by precipitation, high concentrations of various species of microorganisms with little precipitation performance are impossible for biological treatment to be achieved. Thus, the method is limited in terms of loads applicable in terms of BOD (biological oxygen demand) and COD (chemical oxygen demand). In systems with immobilized biomass, the concentration of the biomass (containing the bacteria) is achieved by making bacterial cling into the carrier medium. Sedimentation performance is then no longer an essential criterion, and this technique has a much better purification than standard methods.

Among the most efficient methods based on the principle of purification with immobilized biomass, the inventors have cited those patented and developed by the applicant in a single upflow reactor of granular bed consisting of two zones with different particulate measurements and different biological properties. French Patent No. 76 21246 (Publication No. 2 358 362); French Patent No. 78 30282 (Publication No. 2 439 749); French Patent No. 86 13675 (Publication No. 2 604 990). )).

In the so-called glass biomass technology, the material used as the biofilter is, for example, currently shared methods (French Patent No. 363 510 (1963); British Patent No. 1 034 076 (1962)). References can be made in particular to methods using fluidized beds consisting of products with a density of less than 1, such as expanded polymers according to the present invention, the various implementations of which have formed a number of invention patents (France Patents 330 652, 2 406 664, 2 538 800; U.S. Patent 4 256 573; Japanese Patent 58-153 590 and the like).

The use of such floating materials and fluidized granules is promising on their own, but involves many difficulties and often presents drawbacks. For example, if a material heavier than water (such as sand or similar material) is fluidized, significant energy input is required to pump the liquid and is difficult to manage to maintain the materials inside the reactor. In order to overcome this energy consumption deficiency, it has been suggested to use a fluidized bed containing a hard material having a lower density than water, and intake of air into the base of the fluidized bed but supply of down water (as described herein above). US Patent No. 4 256 573 and Japanese Patent No. 58 153590). However, from a certain downward velocity of water, air bubbles are trapped within the material or otherwise carried along with the liquid flow, making it impossible to properly aerator the reactor.

The difficulty of the prior art is that in a single reactor or biological filter using an upward flow of water and gas, the filtration means and bacterial support media used are fixed bed of particles having a lower density than water with a density of 35-65 kg / m 3. This was solved by the development of the system disclosed in the applicant's application EP0504065. Particular preference is given to using expanded polystyrene having a particle size in the range of 2-6 mm.

The reactor of EP0504065 includes zones for sludge expansion and removal of the media from the bottom to the top and for the settling of loose sludge; At least one air injection device; And a washing water storage zone provided for the removal of the effluent treated at its end at the top of the reactor, as well as a sailing made of the above mentioned layer of light particles, concrete or other perforated material.

Another reactor developed by the applicant is disclosed in EP0347296, where the reactor is equipped with a low fluidized bed and a high fixed bed for filtration. The particles in the layers are comprised of expanded particles having a density of less than one. The particles in the fixed bed are all smaller and lighter than the particles in the fluidized bed.

In addition, a single reactor or biological filter is used in these systems with an upflow of water and gas. For the combination of the two overlapping layers mentioned above, the method according to EP0347296 is lighter than water, but its particle measurement, density and layer height characteristics, on the one hand, do not inject oxygenated gas without proper perturbation of the upper layer. The fluidization of the lower layer during use, on the other hand, uses a changing material such that "automatic" reclassification of the two layers or beds is achieved during the stage of expansion of the light material when it is washed in countercurrent.

In the stopper, these two layers of material, lighter than water, adhere to each other because of their different densities. This classification is maintained while the filter is washed in countercurrent. When air is introduced into the base of the filter by the diffusion device, the air and water mixture passing through the material has a density similar to the particles in the above mentioned sublayer. In this case the lower layer is fluidized by the upward movement of the oxygen gas bubbles, which causes an intense exchange between the gas, the water to be treated and the "biofilm" adhering to the particles of the layer.

For lower fluidized beds, particle measurements can range from 3-15 mm. The bulk mass is generally 300-800 g / l, the bed height ranges from 0.2-2 meters and depends on the type of reactor used; In the upper fixed bed, the average diameter of the light particles is 1-10 mm, while the bulk mass is 20-100 g / l and the height may be 0.5-3 meters. Finally, in the case of the above-mentioned variant, the top layer overmounting the top bed comprises particles having a size of 3-20 mm, a volume mass of 10-50 g / l and a height or thickness of 0.10-0.50 meters.

Particles of light material that can be used as the filtration medium / bacterial support include, for example, closed-cell materials obtained from foamed plastic materials, polyolefins, polystyrenes, synthetic rubber polymers, copolymers, and the like; Light mineral substances such as clay or expanded shale or cellulose products such as wood particles. Granules of such materials can advantageously be in various forms such as balls, cylindrical pods, and the like. Indeed, for the effective performance of the method, it is important to ensure that the density of the light particles used in the context of the invention gradually decreases as it moves from the lower layer (fluid layer) to the upper layer and then to the above-mentioned support layer. For example, the density ranges are each 0.5-0.8 (fluid layer); 0.3-0.1 (fixed layer) and 0.005-0.08 (upper support layer).

In another application FR2741872, Applicant discloses another water treatment reactor in which a fixed bed and a fluidized bed are combined. The reactor has a first filtration zone of rigid PVC material with a fixed 3D structure and a second filtration zone having a lower density than water and filled with a filling material, such as a fixed polystyrene ball, for example. Since a frequent problem with such reactors is particle loss during backwashing in countercurrent, these reactors provide a space between the two zones to allow expansion of the fixed bed of the second filtration zone during washing. Oxygen injection means is placed in this space. Thus, oxygen is injected only above the first zone, which stays oxygen deficient. Air only enters the second zone. In this reactor two different zones are combined, one for denitrification and the other for nitriding.

The particles used in such bioreactors do not provide any protective surface area for the growth of biofilm on the particles because the particles used are small spherical particles. Thus, the biofilm can grow only on the surface of the spherical particles, which is not protected from any damage that may be caused by the collision of the spherical particles.

In contrast, the carriers disclosed in EP0750591 are large and the process efficiency is not significantly reduced by the still larger oxygen limits of the biofilm compared to the small carriers available, and provides a large surface for biofilms that are protected against wear.

The large carrier element of EP0750591 has a structure similar to a turbine wheel with radially inner walls interconnected by outer rings and forming several axial passages. Thus, the large area of the inner surface of the carrier is protected against water with respect to the surface of the other carrier. Moreover, the flow passage allows good flow through the water. Other suitable carriers are disclosed in EP1340720 and EP05785314.

The carrier element of EP0750591 has a density close to that of the water so that the carrier with the biofilm remains suspended in the water in the reactor and moves. This avoids water staying stationary on the carrier and ensures that air can pass through the inner passage of the carrier.

Applicants of the present invention combine the advantages of the arrangements of conventional reactors with the advantages of the carrier types disclosed in, for example, EP0750591, EP1340720 and EP05785314 in order to provide an improved water purification method that exhibits very increased yields. At the same time it is an object of the present invention to provide a reactor which provides higher yields without increasing the volume.

According to the present invention there is provided a reactor and a purification method for improved biological wastewater purification, which are described in more detail below.

The present invention provides a space for expanding and removing sludge having a volume V, a gas injection system located in a lower region close to the bottom of the space for expanding and removing sludge, and an upper portion of the space for expanding and removing sludge. Or to a biological purification reactor comprising a fluid injection system and a biological filter located thereon. The biological filter is packed into a packed bed of particles retained in the lower portion of the reactor by a porous retention ceiling against upward movement, and within the space and for the expansion and removal of the sludge. It contains a volume of mobile particles located above the bottom of the space for expansion and removal.

The packed layer and the particles of the mobile particles are carriers for the microbial membrane.

The mobile particles have a density of 900-1200 kg / m 3, preferably 920-980 kg / m 3. The density of the packed bed particles is 900 kg / m 3 or less, more preferably 500 kg / m 3 or less.

The mobile particles are hollow carriers that include a protective surface area that is protected against collision with the surface of another carrier element.

In another embodiment of the invention, the mobile particles have a total specific surface area of 500-1800 m 2 / m 3, preferably 600-1400 m 2 / m 3, per particle element volume and are designed to allow good flow of water and gas through the carrier. Have flow passages. As used herein, the unit "surface area per particle element volume" means that the surface of the mobile particles is divided by the volume of the particles themselves. In the present application, this does not refer to the unit "surface area per bulk volume of particles" commonly used in the commercial description of the properties of such carriers.

In addition, the mobile particles preferably have a high protective surface area in the range of 300-1600 m 2 / m 3 and preferably 500-1200 m 2 / m 3 per particle element volume. Its length and width can range from 10-70 mm, preferably from 20-45 mm. Its thickness is in the range of 1-30 mm, preferably in the range of 3-20 mm.

In a preferred embodiment of the present invention, the volume V of the space for the expansion and removal of the sludge is 30-80%, preferably 30-55% of the total volume under the porous retention ceiling of the biological purification reactor. In one embodiment, 20-70%, preferably 30-65% of this volume V is filled with mobile particles.

In another preferred embodiment, the particles of the packed bed are expanded particles having a density of 15-100 kg / m 3, preferably 35-90 kg / m 3, more preferably 60-90 kg / m 3 and a particle size of 2-6 mm. Preferably it has a particle size of at least 3 mm to avoid clogging of mobile particles by particles in the packed bed.

In another preferred embodiment, the fluid infusion system comprises a hole. The size of the hole is selected to be smaller than the selected size of the mobile particles such that the particles cannot pass through the hole and are retained by the fluid injection system.

In one preferred embodiment, the biological purification reactor comprises a second gas injection system, which is located in a packed bed of particles.

The present invention also relates to a method for biological purification of wastewater comprising the first step of providing a biological purification reactor as described above.

The second stage of the invention allows water to be biologically purified to pass upwardly through the reactor and through a volume of mobile carrier and the packed bed constituting the biological filter, while at the same time the space for expansion and removal of sludge Injecting gas into and passing the gas through the biological filter in an upward flow direction in the same flow direction with water to be biologically purified.

The third step of the process of the present invention consists in periodically backwashing the packed bed and the mobile carrier using a rapid outflow in the direction of countercurrent flow of treated and stored water at the top of the reactor.

In one embodiment of the method of the present invention, when the biological purification reactor comprises a second gas injection system located in a packed bed of particles, gas is injected into the packed bed through the second gas injection system.

In a preferred embodiment of the process, the backwashing step is carried out at a water outflow rate of 30-100 m / h. Gas is injected during backwash to improve loosening of excess biological sludge. The injection of gas is carried out continuously at an air flow rate of 10-100 m / h, preferably 10-40 m / h, and this series of gases is alternately injected using openings in the backwash water valve, Alternatively, it can be injected simultaneously while the backwash valve is open.

In one embodiment, the method also includes performing a simple miniwash flush operation periodically to loosen solids suspended in the packed bed and the volume of moving particles and to allow longer operation between two backwash cycles. Include.

The invention also relates to a water treatment plant comprising at least one arrangement of bioreactors as described above. Each bioreactor array contains 1-20 in parallel operation. Application of 4-14 bioreactors in one array in parallel operation is preferred for smooth operation.

The water treatment plant according to the invention may comprise a 1-10 bioreactor array.

In another embodiment, the backwash operation in the water treatment plant is carried out with one bioreactor per array at a time. Although only one bioreactor per array can be backwashed at a time, the use of multiple arrays enables backwash operation of more than one bioreactor at a time.

1 shows a cross-sectional view of a bioreactor according to the prior art EP0504065.
2 is a cross-sectional view of a bioreactor according to one embodiment of the present invention.
3 shows a cross-sectional view of a preferred embodiment of the hollow carrier used to form the volume of mobile particles in the present invention.
4A and 4B show perspective views of the bottom of the bioreactor and its optional fluid injection system.
5 is a cross-sectional view of a bioreactor according to one embodiment of the present invention.

According to the drawings provided, the prior art bioreactor 1 shown in FIG. 1 and the two preferred embodiments 1 'and 1 "of the present invention shown in FIGS. 2 and 5 are spaces for the expansion and removal of the sludge underneath them. (2) a packed bed (5) held by the fluid injection system (3), the gas injection system (4) and the porous plate (6) acting as a sail; and finally, the treated water is removed through the outlet (8). It comprises a free upper section 7 which acts as a washing reserve.

The fluid injection system 3 is simultaneously provided as a system for sludge outtake during backwash operation of the bioreactor as indicated by the arrows in both directions in FIGS. 1, 2, 4a, 4b and 5.

The liquid to be treated arrives through the inlet 9 and is introduced into the zone 2 through the valve 12 through the fluid injection system 3 under the gas injection device 4. When a gas is introduced by the gas injection device 4, an intense exchange is made between the gas, the water to be treated and the biofilm which is stuck to the particles. During this operation, the packed bed 5 stays in a non-turbulent state. It is therefore a "fixed bed".

2 and 5, the space 2 for the expansion and removal of the slurry in the bioreactor of the present invention is partially filled with the hollow carrier 10. This is considered to be "volume of movable particles" in the present invention. However, unlike those mentioned above for the packed bed 5, the volume of such mobile particles does not form a fixed bed, but the hollow carrier 10 can move freely. This means that when gas is introduced into the base by the gas injection system 4, the volume of such mobile particles will be turbulent, and the hollow carrier 10 will rotate around in the space 2 by its flow. will be. In addition, since the hollow carrier 10 has a flow through the passage, water and gas not only rotate the carrier in the space 2, but also flow through the hollow carrier 10, such a hollow carrier 10 All internal surface areas of the will be in contact with water and gas. This maximizes the contact of the water to be treated with the biofilm surface present on all surfaces, both the outer and inner surfaces of the hollow carrier 10. The inner surface of the hollow carrier is called a "protected surface" to emphasize the fact that this surface is not damaged by free movement of the carriers in water and the resulting collisions. In contrast, there is a "total surface area" which refers to the total surface area available for biofilm formation on the hollow carrier 10 and thus includes all inner and outer surfaces.

Referring again to FIGS. 1, 2 and 5, due to the accumulation of suspended matter and biological growth in the packed bed 5 and the hollow carrier 10, the material is gradually blocked. The increase in load loss may involve pressure measurements or may involve an increase in liquid level in the load or load loss measurement at the inlet 9.

When the predetermined load loss value is reached, washing of the layer is started. Washing means the removal of excess sludge from the particles of the biofilter, where the excess sludge leaves the bioreactor through a pipe / channel system located at the bottom of the reactor. This pipe system is connected to the flush valve 11. To start cleaning, valve 12 is closed and valve 11 is opened to a predetermined position until the desired cleaning rate is obtained. The rapid outflow of the treated and stored liquid in the direction of countercurrent flow in the upper part 7 of the reactor enables the expansion of the material of the packed bed 5. For the particle size and density of the material of the packed bed 5 as defined above, a washing speed of 30-100 m / h is chosen. This cleaning rate is likewise suitable for the hollow carrier 10 located in the space 2 for expansion and sludge removal.

The volume of the normal expansion zone required for the packed bed 5 during backwashing is less than the volume of the space 2 for expansion and sludge removal.

This allows the hollow carrier 10, which moves freely during backwash, to rotate mainly towards the bottom of the reactor, thus leaving enough space for particles in the packed bed to flow without being limited in their movement. In very rare cases where particles from the positioned packed bed 5 are moved further down towards the sludge discharge system 3, the movement of the hollow carrier 10 downwards is also referred to as an additional protective grid. Can act "

It will be appreciated that the fluid injection system 3 as described above is provided simultaneously as a system for sludge outtake during backwash operation of the bioreactor as indicated by the arrows in both directions in FIGS. 1, 2, 4a, 4b and 5. .

The space (2) is generally provided in a relatively high volume compared to the total volume under a porous retention ceiling of about 30-50% of the biological purification reactor in the prior art approach to avoid particle loss during the backwashing process. do. However, in the present invention, this space fills 20-70%, preferably 30-65% of this volume with the hollow carrier 10, thus maintaining a more biologically active surface while maintaining the same total volume of the bioreactor. It is used more efficiently by providing Considering the prior art approach, minimizing the volume of the free space 2 is such that the space is generally considered necessary for expansion of the packed bed particles during backwashing as described above, resulting in more particle loss in the packed bed during backwashing. Is expected to cause. However, according to the invention, since the size of the hollow 15 (shown in FIGS. 4A and 4B) of the fluid injection system 3 is chosen to be smaller than the minimum diameter of the hollow carrier used, the hollow carrier 10 is a fluid. It is held in the reactor by the injection system 3. Thus, the fluid injection system 3 acts simultaneously as a protective grid which prevents the hollow carrier 10 from washing away the reactor. The preferred size for the hollow 15 of the fluid injection system 3 is in the 6-60 mm diameter range.

At the same time, the hollow carrier 10 moving downwards during backwashing acts as an additional protective grid that inhibits the particles of the packed bed 5 from reaching the sludge discharge system 3. Smooth operation of the reactor of the present invention, in which the hollow carrier provides such an extra barrier that prevents particles of the packed bed 5 from exiting the reactor, is of great importance. In this regard, it is very important to carefully select the correct combination of hollow carrier and particles for the packed bed. Particles in the packed bed should be chosen such that they cannot enter the internal flow passages of the hollow carriers, which can cause clogging of the hollow carriers and reduce the efficiency of the reactor. This means that the particle size of the packed bed should be larger than the maximum internal flow passage present in the hollow carrier, or conversely the hollow carriers should be chosen such that their internal flow passages are smaller than the minimum particles of the packed bed.

Another important parameter to keep in mind when selecting the appropriate hollow carrier and particles for the packed bed is the density of the particles. Since the density varies with temperature and pressure, the density range of the present application is defined at 4 ° C. to standard atmospheric pressure. As mentioned above, the density of the hollow particles is in the range of 900-1200 kg / m 3, preferably 920-980 kg / m 3. The density of the packed bed particles is 900 kg / m 3 or less, more preferably 500 kg / m 3 or less. This minimizes the mixing of the two types of particles during normal operation and backwashing.

In a preferred embodiment, the density of the packed bed particles is in the range of 15-100 kg / m 3, preferably 35-90 kg / m 3, more preferably 60-90 kg / m 3. This low density ensures that the particles in the packed bed float up towards the water surface if not retained. Thus, the particles return to their position very quickly within seconds after retaining sailing, while the higher density hollow particles remain suspended and transported in the water under the packed bed. In addition, due to the low density of the particles in the packed bed, the upward force of these particles is very high. Thus, the packed bed is very compact and almost completely fixed. The filtration performance of this packed bed is therefore very high. In addition, the density difference between these two different types of particles ensures that the mixing of the two types of particles is very limited during normal operation of the reactor.

In the present invention, no additional air or water upflow is required to achieve the formation of the two types of particles and the formation of a high compact packed bed. Thus, there is no need to control and regulate the flow to keep the bioreactor itself in action. Thus, the flow can be adjusted solely to achieve optimal water treatment efficiency. In contrast, conventional prior art reactors containing fixed and fluidized beds of particles having a density closer to the density of water generally allow for additional upflow of air or water to keep the fluidized bed lower and the packed bed higher. in need. In addition, the combination of the two layers after backwashing is not achieved as quickly as for the packed bed and mobile carrier in the present invention.

An additional disadvantage of using particles having a density closer to that of the water and thus having a less compact fixed bed is that the injected air forms "pathways" in the fixed bed when air is injected for the purification of the waste water. It can be done. This "path" will reduce the treatment efficiency of the fixed bed. In the present invention, this does not occur. Moreover, due to the fact that the packed bed is very compact, it takes longer for air bubbles to travel through the packed bed. This increases the time the oxygen moves from air to water, thus increasing the activity of the biofilm.

Referring back to the operation of the bioreactors shown in FIGS. 2 and 5, a rapid change in backflow flow is carried along the solids stored in interstitial spaces, removing excess biomass collected on the surface of the material. Although possible, the above-mentioned speeds make it possible to preserve the active biofilm on the material. After draining the reservoir 7 and closing the balance 11, it is possible to resume the supply by opening the valve 12 to a load similar to that used before cleaning.

Another advantage of using backwash backwash is that the particles in the upper part of the packed bed do not come into contact with the pollutant because only the purified water reaches the packed bed portion during operation, while the main part of the pollutant remains in the lower portion during operation. Will be. During backwashing, the contaminants are then moved back down so that the top of the packed bed does not come into contact with the contaminants during backwashing. In contrast, co-current backwash allows all packed bed particles to come into contact with the total contaminants, thereby reducing the efficiency of the packed bed. It is also possible for contaminants to reach and clog the retention sail when co-forced backwashing is used. The retaining sailing remains extra during backwash backwashing.

If desired, the recycling of the purge effluent by the pump may improve the distribution or enable the supply of nitrates in the prefiltration zone.

In order to extend the time period between the washes, a very brief flushing operation by the opening of the valve 11 may be performed periodically to loosen the material, allowing impurities to penetrate deeper into the filtration layer. This mini-clean operation will further clog the bottom of the filter, which is further filled with suspended solids. Rapid flushing operation can be performed in such a way as to provide a balanced load loss across the height of the filtration bed.

Continuous gas injection can be maintained during cleaning to assist in unclogging of the hollow carrier as well as the packed bed. During backwash, continuous air will shake the hollow carriers and inhibit their blockage. A series of air can be introduced, for example, during a pause in washing water injection as described in the preferred embodiment below, or continuously while the washing water is running continuously.

In a preferred embodiment of the invention, the backwashing procedure comprises the following steps:

a) pre-washing with water alone

This operation consists of pre-washing (water alone) by opening the wash water drain valve for a predetermined time period, T0, to loosen the sludge before injecting air for mixing, while the filter is switched out. .

b) loosening sludge with air alone

This step consists of injecting air into the air system, mixing excess sludge and loosening it while the wash water drain valve is shut off. This phase lasts for T2.

c) Pausing step

Pause to allow loosened material to settle for time T14

d) cleaning step by exchange of water phase and air phase

This step

-Water alone during T1

-Air alone during T2

-Pause during T14

-Water alone during T1

-Air alone during T2

-Pause during T14

It consists of a continuous injection of.

These steps are designed to loosen all excess sludge and empty it partially towards the filter media. To obtain a more complete wash, additional water scour step (predetermined time T1) and air scour step (predetermined time T2) and rest (predetermined time T14) can be added. .

e) rinsing with water alone

This step consists of emptying the residual excess sludge with a downward flow of water during time T3.

The backwash sequence ends when T3 elapses. Depending on the actual filtration rate, the filter is returned to filtration mode or enters standby mode.

One of the many advantages of using freely moving hollow carriers in place of a second fluidized bed or packed bed in the reactor is that only a small additional pressure loss headloss is introduced by such mobile carriers during normal operation of the bioreactor. . This reduces the energy consumption for aeration of the bioreactor.

Finally, since the gas bubbles break into smaller bubbles when contacted with freely moving hollow carriers at the bottom of the reactor, the hollow carriers are provided for improved distribution and slower movement of the gas upwards relative to the packed bed. . This ensures an improved supply of gaseous biofilms, resulting in higher efficiency of the reactor.

In addition, the hollow carriers reduce clogging of the packed bed with total suspended solids (TSS) because biomass generated and accumulated on the hollow carriers is removed during backwash. Moreover, because less CDD reaches the packed bed, the growth of biomass is slower on packed bed particles than in a conventional bioreactor as shown in FIG. 1 where only packed bed is used. This minimizes the frequency of backwashing and at the same time minimizes the wash water load required for disposal.

3 is a side view of an exemplary hollow carrier suitable for use in the present invention. This structure represents the outer and inner walls of the carrier suitable for the growth of the biofilm. As can be readily appreciated from this figure, the biofilm growing on the inner surface of the carrier will be protected from being damaged through collisions with other carriers during operation of the bioreactor.

4A and 4B, two optional fluid injection systems are shown. In FIG. 4A, the fluid injection system made of concrete is shown according to the fluid injection system shown in the bioreactor of FIG. 2. The fluid injection system may be made of, for example, concrete or other suitable material known in the art. In the lower part of the bioreactor 13, an inlet channel 14 having a hole 15 is formed. In an alternative solution, FIG. 4B, a pipe 16 with a hole 15 is inserted at or below the bioreactor. Such pipes can be made, for example, of steel or plastic, or other suitable material known in the art. In both implementations, the water injection channel also acts as a sludge discharge channel during backwashing as indicated by arrows pointing in both directions. The size of the aperture 15 is chosen to be smaller than the selected size of the mobile particles 10 such that the particles do not pass through the aperture 15 and are retained by the fluid injection system 3. If the mobile particles 10 are pressed towards the bottom of the reactor, they are retained by the fluid injection system 3 during backwash, so that the loss of beneficial mobile particles 10 is avoided.

FIG. 5 shows an alternative implementation of the reactor of the present invention, which differs only from including a second air injection system 17 located in the packed bed 5 and operates in the same way as the bioreactor shown in FIG. 2. When the bioreactor is operated and air introduced through the air injection system 4 and the second air injection system 17, the packed bed 5 is filled with an aeration zone 19 in the packed bed as shown in FIG. It will include a non-aeration zone 18. Within the aeration zone 19, nitriding with O ₂ can take place from the injected air. If it does not occur that the aeration of the air injection system (4), an oxygen-free zone, that is, NO ₃ -N zone contains oxygen derived from the sole, the oxygen of the carbon removal of NO ₃ -N in place of oxygen supplied by aeration It is possible to ensure that the nitrate is removed (denitrified) when used for the purpose. It is understood that the second air injection system 17 is not provided for air injection during backwashing, but only for air injection during normal operation of the bioreactor. As described above for the above implementation with only the air injection system 4, and also in this embodiment, when air is additionally or exclusively introduced through the air injection system 17, the gas, the water to be treated and the particles to be treated. Intensive exchange is obtained between biofilms adhering to the film. During this operation, the packed bed 5 stays in a non-dynamic state and is thus a "fixed bed".

According to an advantageous embodiment of the method of the invention, one or more arrangements of the above described bioreactors are set in parallel in one large water treatment plant. Each array of parallel bioreactors in one large water treatment plant may contain 1-20 bioreactors. However, an amount of 4-14 bioreactors per array is preferred. A 1-20 bioreactor array can be implemented in parallel in one water treatment plant.

Each bioreactor array has one common feeder supplying load columns individually associated with each bioreactor. This is because other load columns can compensate for the pressure, so that excess pressure in the bioreactor can be suppressed if one column is blocked.

In addition, the water reserves for the purified water of each bioreactor are interconnected and form one large compartment for the purified water on top of each array. Thus, the purified water of all bioreactors running in one arrangement provides a water stream for backwashing the blocked bioreactor, where backwashing takes place.

It is preferable that only one bioreactor is backwashed at a time while other bioreactors are present during normal water treatment operation for smooth operation of the water treatment plant of the present invention. Only one bioreactor per array can be backwashed at a time, but the use of multiple arrays in parallel allows backwashing of one or more bioreactors per plant at a time, which increases the efficiency of the treatment plant.

Example

As shown in FIG. 2, a test run was performed to determine the removal efficiencies of total suspended solids and soluble COD in the biological purification reactor of the present invention.

The reactor used for the test-run was a 6.5m high 0.9m diameter column. The reactor had a 3.5m packed bed using a spherical medium having a diameter of 4.5 mm and a density of 55 kg / m 3. The volume below the packed bed with a height of 1.9 m was filled with 35% hollow carrier with a density of 960 kg / m 3 and a protective surface area of 800 m 2 / m 3. In the reactor The municipal wastewater produced from the primary settler of Thibaut des Vignes WWTP (France) was fed and the total suspended solids (TSS) and soluble chemical oxygen demand (filtered COD) content of the wastewater was measured before and after the reactor was measured.

The reactor was seeded with 1 m / h inlet flow for 3 weeks and the load on the reactor was increased in several stages when sufficient activity was recorded. 24 hour average samples were taken during the highest load of the plant.

The test run results are shown in Tables 1 and 2 below. The results are shown in comparison with standard design values and results predicted from the biological purification reactors disclosed in the prior art as shown in FIG. 1.

Comparison of removal efficiency of total suspended solids (TSS) by biological purification reactors disclosed in the prior art (FIG. 1) and the present invention (FIG. 2) TSS load
(kg / ㎥ / d) TSS Inflow
(mg / l) TSS emissions
(mg / l) Removal rate
(%) Cycle
(h) Prior Art Reactor (FIG. 1) 2.7 100 25 75 24 Reactor of the invention (FIG. 2) 6 200 70 65 24

Comparison of removal efficiency of COD by the biological purification reactor disclosed in the prior art (FIG. 1) and the present invention (FIG. 2) CODsol load
(kg / ㎥ / d) CODsol inflow
(mg / l) CODsol emissions
(mg / l) Removal rate
(%) Cycle
(h) Prior Art Reactor (FIG. 1) 2.9 200 50 75 24 Reactor of the invention (FIG. 2) 6 170 60 65 24

St. Thibaut des Vignes WWTP has a high degree of industrial influent entering WWTP, which should be noted to form a relatively large non-degradable soluble COD fraction in the influent wastewater. Thus, the amount of soluble CDD in the influent is somewhat higher than the amount expected from more "classical" municipal wastewater, which results in lower achieved removal rates for these parameters. This “classic” municipal wastewater was disclosed in the prior art and used to obtain efficiency data for the biological purification reactor shown in FIG. 1.

Claims (16)

A method of biologically treating wastewater in a bioreactor and removing suspended solids from the wastewater,
In purge mode:
Directing the wastewater to the lower part of the bioreactor via a wastewater injection system comprising an array of openings to allow the wastewater to be injected into the bioreactor;
Injecting air into the bioreactor;
Directing wastewater and air upward through an expansion space containing a movable hollow biofilm carrier and through a flow passage passage within the movable hollow biofilm carrier;
Directing wastewater and air upward from the expansion space through a packed bed of biofilm carrier disposed on the expansion space and having a density less than that of the movable hollow biofilm carrier contained in the expansion space, and wherein Wherein the biofilm carrier of the packed bed is larger than the passage flow passage of the movable hollow biofilm carrier;
Retaining a packed bed of biofilm carrier in a bioreactor under a porous screen;
Forming a biofilter with a packed bed of biofilm carrier and a movable hollow biofilm carrier;
As the wastewater moves upward through the expansion space and the packed bed of biofilm carrier, collecting suspended solids in the biofilter and collecting the treated wastewater in the space within the bioreactor
It includes, and
In backwash mode:
Removing the suspended solids held by the biofilter via backwashing, wherein at least a portion of the treated waste water retained in the upper space in the bioreactor is used as backwashing material;
Directing the backwash through the packed bed of the biofilm carrier and through the expansion space and the movable hollow biofilm carrier contained therein, and expanding the packed layer of the biofilm carrier into the expansion space;
Entraining the suspended solids retained by the biofilter into the backwash;
Draining backwashing containing suspended solids from the bioreactor by directing the backwashing and entrained suspended solids through an opening arrangement in the wastewater injection system;
Suppressing the release of hollow biofilm carriers that are movable with the backwash; And
Forming a protective grid in the bioreactor with a movable hollow biofilm carrier, preventing the biofilm carrier in the packed bed from passing through the protective grid of the movable hollow biofilm carrier, and backwashing through the opening arrangement in the wastewater injection system Draining from the bioreactor with water
Including, method.
The method of claim 1,
Further comprising backing the biofilter through a series of steps in the following order:
Step 1: loosening suspended solids held in the biofilter by initiating a pre-cleaning step, wherein the pre-washing step is capable of carrying only a packed bed of biofilm carrier and a removable wastewater retained in the bioreactor Comprising directing downward through the hollow biofilm carrier;
Step 2: after the pre-cleaning step, further loosening the suspended solids retained in the biofilter by injecting air into the biofilter;
Step 3: after step 2, the suspended solids are precipitated by performing a pause step for a selected period of time during which no air or treated waste water is directed through the biofilter;
Step 4: cleaning the biofilter by using an alternating process comprising a treated wastewater backwashing process and an air injection process, wherein in the first step of step 4, the treated wastewater is directed downward through the biofilter Cleaning the suspended solids therefrom, in a second step of step 4, only air is injected into the biofilter, where the first and second steps are repeated as part of step 4; And
Step 5: after step 4, rinsing the biofilter with the treated wastewater.
The method of claim 1,
During the purification mode, the movable hollow biofilm carrier is not fluidized.
The method of claim 1,
The biofilter is backwashed at a washing speed of 30-100 m / h.
A bioreactor operating in a first mode of treating wastewater and removing suspended solids from the wastewater, and operating in a second mode of performing backwash operation,
In the first mode, the bioreactor is
A packed layer of a biofilm carrier disposed in the bioreactor;
An expansion space in the bioreactor under the packed bed of biofilm carrier;
A movable hollow biofilm carrier disposed in an expansion space below the packed bed of the biofilm carrier and having a density greater than that of the packed bed of the biofilm carrier:
Wherein the movable hollow biofilm carrier comprises a smaller passage flow passage than the biofilm carrier of the packed bed;
An air injection system for injecting air into the bioreactor;
An opening arrangement and configured to inject wastewater into the reactor, wherein the wastewater and air are wastewater comprising an opening arrangement that moves upward through the expansion space, a flow passage passage through the movable hollow biofilm carrier, and a packed bed of biofilm carrier Injection system
It includes;
Wherein the opening arrangement of the wastewater injection system is smaller than the movable hollow biofilm carrier;
Wherein the packed bed of biofilm carrier forms at least a portion of the biofilter for removing suspended solids from the wastewater moving upwardly through the biofilter;
In the second mode, the bioreactor is
Wherein the wastewater injection system and its opening arrangement are also configured to discharge backwash and suspended solids incorporated into the backwash during the backwash operation; And
A protective grid formed at the bottom of the bioreactor by a movable hollow biofilm carrier, which generally inhibits passage of the packed layer of the biofilm carrier through the protective grid and is discharged with backwash through an array of openings in the wastewater injection system. Being protected grid
Containing, bioreactor.
The method of claim 5,
The biofilm carrier of the packed bed has a density of 60-90 kg / m 3, wherein the biofilm carrier of the packed bed is expanded particles having a particle size of 2-6 mm.
The method of claim 5,
The wastewater injection system includes a series of long and spaced channels extending adjacent the bottom of the bioreactor, wherein an opening arrangement of the wastewater injection system is formed in the series of channels.
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